NEW YORK (Reuters) - The bombing of a packed London commuter train on Friday prompted officials to beef up security on New York City's subway system, major commuter rail networks, at airports and other locations.

The Metropolitan Transportation Authority, which operates mass-transit lines in New York City and the Long Island Rail Road and Metro-North commuter lines, said it was closely monitoring the investigation of the fiery blast that injured 29 people in a West London underground station.

The MTA will expand bag screening and deploy extra police patrols on the LIRR and Metro-North, as well as in midtown Manhattan's Grand Central Terminal and Pennsylvania Station, "out of an abundance of caution," spokesman Kevin Ortiz said.